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J/ApJ/787/151         Fitted jet components in BL Lacertae        (Cohen+, 2014)

Studies of the jet in BL Lacertae. I. Recollimation shock and moving emission features. Cohen M.H., Meier D.L., Arshakian T.G., Homan D.C., Hovatta T., Kovalev Y.Y., Lister M.L., Pushkarev A.B., Richards J.L., Savolainen T. <Astrophys. J., 787, 151 (2014)> =2014ApJ...787..151C (SIMBAD/NED BibCode)
ADC_Keywords: BL Lac objects ; Active gal. nuclei Keywords: BL Lacertae objects: individual: BL Lacertae - galaxies: active - galaxies: jets - magnetohydrodynamics, MHD - waves Abstract: Parsec-scale VLBA images of BL Lac at 15 GHz show that the jet contains a permanent quasi-stationary emission feature 0.26 mas (0.34 pc projected) from the core, along with numerous moving features. In projection, the tracks of the moving features cluster around an axis at a position angle of -166.6° that connects the core with the standing feature. The moving features appear to emanate from the standing feature in a manner strikingly similar to the results of numerical two-dimensional relativistic magneto-hydrodynamic (RMHD) simulations in which moving shocks are generated at a recollimation shock (RCS). Because of this, and the close analogy to the jet feature HST-1 in M87, we identify the standing feature in BL Lac as an RCS. We assume that the magnetic field dominates the dynamics in the jet, and that the field is predominantly toroidal. From this we suggest that the moving features are compressions established by slow and fast mode magneto-acoustic MHD waves. We illustrate the situation with a simple model in which the slowest moving feature is a slow-mode wave, and the fastest feature is a fast-mode wave. In the model, the beam has Lorentz factor Γbeamgal∼3.5 in the frame of the host galaxy and the fast mode wave has Lorentz factor ΓFwavebeam∼1.6 in the frame of the beam. This gives a maximum apparent speed for the moving features, βapp=vapp/c=10. In this model the Lorentz factor of the pattern in the galaxy frame is approximately three times larger than that of the beam itself. Description: The MOJAVE program (Lister & Homan 2005, J/AJ/130/1389, Monitoring of Jets in Active Galactic Nuclei with VLBA Experiments) is conducting regular observations of about 300 sources with the VLBA at 15 GHz (Lister et al. 2013, J/AJ/146/120). The observing cadence varies from a few weeks for the most variable sources to about three years for slowly changing ones. BL Lac varies rapidly and we are currently observing it every one to two months. Here we present results from 55 epochs between 1996.2 and 2013.0. For this paper we have also added results from other programs whose results are in the VLBA archives, for a total of 110 epochs, all observed on the VLBA at a frequency near 15.3 GHz. Objects: ---------------------------------------------------------- RA (ICRS) DE Designation(s) ---------------------------------------------------------- 22 02 43.29 +42 16 40.0 BL Lacertae = NAME BL Lac ---------------------------------------------------------- File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file table1.dat 49 616 Fitted Jet Components of BL Lac
See also: J/AJ/130/1389 : Linear polarization of AGN jets at 15GHz (Lister+, 2005) J/AJ/137/3718 : 15GHz monitoring of AGN jets with VLBA (Lister+, 2009) J/ApJ/722/L7 : Fermi/LAT detected MOJAVE AGNs (Pushkarev+, 2010) J/ApJ/742/27 : 15GHz and jet properties of MOJAVE blazars (Lister+, 2011) J/AJ/146/120 : MOJAVE. X. Parsec-scale kinematics of AGNs (Lister+, 2013) Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 2 I2 --- ID [0/39] Component identifier; zero for core component 4 A1 --- f_ID [a] Flag on ID (1) 6- 15 A10 "date" Date Date of the observation 17- 20 F4.2 Jy I Flux density at 15 GHz 22- 25 F4.2 mas r Distance from the core 27- 33 F7.2 deg PA [] Position angle with respect to core 35- 38 F4.2 mas MajAxis FWHM major axis of fitted Gaussian 40- 43 F4.2 --- Ratio Axial ratio of fitted Gaussian 45- 49 F5.2 deg MajPA ? Major axis position angle of fitted Gaussian
Note (1): Flag as follows: a = Fewer than 5 epochs, or r>4 mas.
History: From electronic version of the journal References: Cohen et al., Paper II, 2015ApJ...803....3C
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 30-Jun-2017
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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